The invention relates to a gas bag restraint device comprising a gas bag module.
A known gas bag restraint device in which a center section of a front wall of the gas bag is fastened to the module is described in DE 197 49 914 A1. The gas bag used there has, in the inflated state, an annular chamber which is to be filled with gas. The center section is either fastened directly to the gas generator or, if gas is blown in via the steering column, is permanently fastened to the module via a sleeve, i.e. it maintains fastened to the module even in the inflated state of the gas bag and is, therefore, prevented from a free movement while unfolding.
The invention provides a gas bag restraint device, in which the gas generator housing is subjected to lower mechanical stresses than in the prior art and in which the gas bag is subjected to lower thermal stresses than in the prior art. This is achieved in a gas bag restraint device which comprises a gas bag module with an outlet opening. The module has a gas generator and a gas bag, the latter including a front wall with a center section. This front wall onto which an occupant who is to be restrained can strike in a case of restraint has a depression defined by the center section of the front wall being permanently fastened to the module and, on inflation of the gas bag, is prevented from a free movement. The restraint device further comprises a module covering closing an outlet opening. A holding part is provided surrounding the gas generator and fastened to the module, on which holding part the center section is fastened. Preferably the holding part is a cup-shaped diffusor having a base and which, with an underside of the base pointing to the module covering, is turned over the gas generator to be attached to the module, the center section being fastened to the base of the diffusor. In the device proposed, a spacing is achieved between the gas generator and the gas bag fabric by the holding part, so that the gas bag fabric does not have the gas flowing directly against it and is thus subjected to lower stresses. Furthermore, the force necessary for holding back the center section is also not introduced into the gas generator housing, which in any case is subjected to high stresses on inflation of the gas bag. Rather, the force summoned up by the holding back of the center section is introduced into the holding part. By the diffusor being constructed in a cup shape and being turned over the gas generator, nevertheless a compact construction is produced.
The center section can be prevented not only from a free but, preferably, from any movement.
Preferably, the diffusor is not only spaced apart from the gas generator radially but also axially, namely in the region of the base, so that between the housing of the gas generator and the diffusor an equalizing chamber for gas can be formed.
The fastening of the center section can take place for example through a fastening of a metal emblem, visible from outside the covering, on the holding part. The fastening of the heavy metal emblem therefore has a dual function, by on the one hand serving to hold back the emblem and on the other hand also to hold back the center section. The metal emblem can also prevent a section of the module covering, lying immediately beneath the emblem, from swiveling on opening of the module covering, so that in this embodiment the center section is gripped between the holding part and the underside of the module covering.
According to another development, the module covering has a section which adjoins the center section. This section is permanently fastened to the holding part and the fastening of this section also serves for fastening the center section.
Preferably, the holding part and the gas generator project into the interior of the gas bag, so that between the module housing and the diffusor an annular space is produced to accommodate the annular, folded gas bag package.